I. Field of the Invention
The present invention relates generally to implantable medical devices having external electrical connections and electrical feed-throughs and, more particularly, to the provision of a pre-built modular sub-assembly interconnect system for a header module such as are found in implantable pulse generators (IPG's) associated with cardiac rhythm management and other hermetically sealed implantable medical devices.
II. Related Art
Implantable medical devices of a class having electrical circuit components are well known in the medical field. These include cardiac rhythm management devices which commonly include a pacemaker unit which, in turn, includes sensing and control circuitry, together with a power supply, protectively housed in a hermetically sealed case or can in combination with one or more conductive electrical leads designed to connect to the patient's heart muscle tissue, the activity of which is to be sensed and stimulated. To maintain the integrity of the components in the sealed case, provision must be made for hermetically sealed passage of electrical conductors to the exterior for connection to the leads and ultimately to tissue of interest. This has been typically accomplished by using connector blocks and associated feed-through conductors located external to the IPG housing which, themselves, are typically placed within a sealed header structure of medical grade polymer material.
While great strides have been made in improving the sophistication of the pacemaker devices themselves, the assembly and testing of the devices has remained relatively dependent on the skill of the assembly workers. Attempts have been made in the art to simplify the assembly process and to improve the acceptance rate of completed devices which undergo rigorous testing once assembled. In U.S. Pat. No. 5,282,841, for example, a ribbon conductor set or harness is provided to facilitate connection of feed-through terminal conductors to corresponding connector blocks in the header in which the individual ribbon conductors leads can be shaped to a three-dimensional geometry for ease of assembly. The assembled or fully interconnected unit is thereafter subjected to an over molding or coating step in which an entire epoxy head is cast over the assembly to encapsulate and seal the connecting components. That system, however, still depends on the skill of workers for assembly and requires extensive over molding. Furthermore, the electrical integrity of the unit cannot be tested until it is completely assembled.
U.S. Pat. No. 6,205,358 B1 discloses a pre-formed header module in combination with a ribbon connector harness which is assembled and placed between feed-through pins on the side of the sealed enclosure and the header module and thereafter captured in an over molding or backfilling step using medical grade polymer. This system also suffers from similar drawbacks to those described above.